Typically, fluid vane motors comprise a housing having a cylindrical bore closed by end plates and a rotor mounted for rotation within the bore. The rotor is in the form of a solid cylindrical billet of metal with longitudinally extending slots formed about its periphery. The axis of rotation of the rotor is parallel to but offset from the longitudinal axis of the housing. A plurality of vanes are supported in respective longitudinal slots in the rotor in a manner so as to allow movement in the radial direction. Fluid chambers are formed between adjacent vanes, the volume of the chambers varying as the rotor rotates. When functioning as a pump, the chambers act to displace fluid from an inlet in the housing to an outlet, and when acting as a motor, the chambers allow for the release of pressure of a pressurised fluid to cause rotation of a shaft attached to the rotor.
Conventional fluid vane motors/pumps are notoriously inefficient due to leakage of fluid between adjacent chambers via leakage paths formed about the periphery of the vanes as well as through the rotor itself. Additionally, high frictional losses occur due to the substantial contact area between the peripheral edges of the vanes and end plates of the housing.